REDUNDANT CONTROLLER DIAGNOSIS USING A PRIVATE LUN

摘要

Methods and associated apparatus within a RAID subsystem having redundant controllers define a private LUN as a data storage area known and accessible to all controllers in the system and used by them for diagnostic purposes. The methods involve sending a diagnostic write command to a first controller with instructions for it to write test data to the private LUN. This first controller writes this test data to the private LUN. A second controller, in response to another diagnostic command, then reads this test data from the private LUN and compares it to expected values provided in the diagnostic command. Using the results, it can then be determined which controller, if any, failed. If the first controller fails, then the second controller takes over ownership of portions of the data storage area assigned to the first controller. The private LUN is preferably striped across all channels used by the controllers to communicate to commonly attached disk drives. This allows the diagnostic process to test disk channel data paths in determining whether a controller has failed. The test data preferably include a data portion and a redundancy portion to enable testing of redundancy computations within the controllers. In an alternate embodiment, a host computer attached via an interface in common with the redundant controllers initiates and controls the diagnostic process to enable testing of the host/controller communication paths. Timed event messages (e.g., watchdog timer features) may be used in conjunction with other methods of the invention to further enhance failure detection.